Carbonyl fluoride has been conventionally produced by a process comprising allowing phosgene to react with a fluorinating agent such as hydrogen fluoride or antimony trifluoride or a process comprising allowing carbon monoxide to react with silver difluoride (Japanese Patent Laid-Open Publication No. 116216/1999). In the carbonyl fluoride produced by the above processes, however, by-products such as hydrogen chloride or silver fluoride are contained. In order to use this carbonyl fluoride as a cleaning gas for a plasma-CVD apparatus that is used in a semiconductor manufacturing process, it is necessary to highly purify the crude carbonyl fluoride obtained by the above processes.
It is known that COF2 can be produced by allowing carbon monoxide to directly react with fluorine (Handbook of Preparative Inorganic Chemistry, Vol. 1, 2nd ed., pp. 206-208, edited by Georg Brauer (Translation editor), Academic Press, New York (1963)). However, it is said that if reaction of fluorine is carried out in a carbon monoxide atmosphere in this process, there is a risk of fierce explosion, and therefore, a process of allowing carbon monoxide to directly react with fluorine under the conditions of excess fluorine is usually used. In this case, carbon tetrafluoride (CF4) is formed as a by-product. This CF4 has an extremely high global warming potential (value of integral time of 100 years) of 5,700 times that of CO2 and has a problem of a fear of harmful impact on the environment. Accordingly, development of a process for producing carbonyl fluoride wherein formation of CF4 is suppressed has been desired.
In the conventional process for producing carbonyl fluoride, further, carbon monoxide and fluorine are allowed to react with each other under the conditions of excess fluorine, so that in the crude carbonyl fluoride obtained after the reaction, fluorine is frequently contained. Both carbonyl fluoride and fluorine are gases at ordinary temperature, and in order to separate them, it is necessary to liquefy or solidify one of these components by a low-temperature treatment, a pressure treatment or the like to separate it from the other component.